KR20110119621A - Method for production of styrene from toluene and methanol - Google Patents

Abstract

A method is described for preparing styrene by converting methanol in the reactor to formaldehyde and then reacting the toluene with the formaldehyde to form styrene in a separate reactor.

Description

METHOD FOR PRODUCTION OF STYRENE FROM TOLUENE AND METHANOL}

The present invention relates to a method for producing styrene.

Styrene is an important monomer used in the manufacture of many plastics. Styrene is generally prepared by making ethylbenzene and then dehydrating to produce styrene. Ethylbenzene is generally formed by one or more aromatic transformations, including alkylation of benzene.

Aromatic conversion processes that are generally performed using molecular sieve catalysts are well known in the chemical processing industry. This aromatic conversion process involves the alkylation of aromatic compounds such as ethylene and benzene to produce alkyl aromatics such as ethylbenzene. Typically the alkylation reactor can produce a mixture of monoalkyl and polyalkyl benzene, which can be combined with a transalkylation reactor for the conversion of polyalkyl benzene to monoalkyl benzene. The transalkylation process operates under conditions that result in disproportionation of the polyalkylated aromatic fractions, which can produce products with improved ethylbenzene content and reduced polyalkylated content. If both alkylation and transalkylation processes are used, two separate reactors, each with its own catalyst, may be employed for each of the processes.

Ethylene is obtained primarily from thermal cracking of hydrocarbons such as ethane, propane, butane or naphtha. Ethylene may also be produced and recovered in various purification processes. Pyrolysis and separation techniques for the production of relative pure ethylene can be an important part of the total cost of ethylbenzene production.

Benzene may be obtained from hydroalkylation of toluene, which involves heating a mixture of excess hydrogen and toluene to an elevated temperature (eg, 500 ° C. to 600 ° C.) in the presence of a catalyst. Under these conditions, toluene can undergo a dealkylation reaction according to the formula: H ₆ H ₅ CH ₃ + H ₂ → C ₆ H ₆ + CH ₄ . This reaction requires energy input and can produce methane as a by-product, as shown in the equation above, which can typically be separated and used to heat the fuel for the process.

In view of the above, it is desirable to provide a styrene production method that does not rely on expensive separation techniques such as pyrolysis and ethylene feed. It is also desirable to avoid the process of converting toluene with intrinsic cost to benzene and the loss of carbon atoms forming methane. It is preferred to produce styrene without the use of benzene and ethylene as feed streams.

One embodiment of the present invention provides one or more second reactors for converting methanol into formaldehyde in one or more first reactors to form a first product stream comprising formaldehyde and for forming a second product stream comprising styrene. Is a process of reacting toluene and formaldehyde. The first product stream may comprise one or more of hydrogen, water or methanol. Methanol can be separated from the first product stream and recycled to the one or more reactors.

The process may include using one or more oxidation reactors to convert methanol into formaldehyde and water to form the first product stream. The process may optionally include using one or more dehydrogenation reactors to convert methanol into formaldehyde and hydrogen to form the first product stream.

The second product stream may comprise one or more of toluene, water or formaldehyde. If present, toluene and / or formaldehyde may be separated from the second product stream and recycled to one or more second reactors. The one or more second reactors may comprise a reaction zone at reaction conditions containing a catalyst for reacting toluene and formaldehyde to form styrene. The process may include sending the first product stream to a separation step to separate formaldehyde from the first product stream.

Another embodiment of the present invention is a process for preparing styrene by converting methanol into formaldehyde in one or more first reactors to form a first product stream comprising one or more of formaldehyde, hydrogen, water or methanol. The first product stream proceeds to a first separation step for separating formaldehyde from the first product stream. The separation step may comprise a membrane for removing hydrogen from the first product stream.

Toluene and formaldehyde are reacted in one or more second reactors to form a second product stream comprising one or more of styrene, toluene, water, or formaldehyde. The second product stream proceeds to a second separation step for separating styrene from the second product stream. Methanol present can be separated from the first product stream and recycled to the one or more first reactors. If present, toluene and formaldehyde may be separated from the second product stream and recycled to the one or more second reactors.

The process may include converting methanol into formaldehyde and water using one or more oxidation reactors to form a first product stream. The process may include converting methanol into formaldehyde and hydrogen using one or more dehydrogenation reactors to form a first product stream. The one or more second reactors may comprise a reaction zone at reaction conditions containing a catalyst for reacting toluene and formaldehyde to form styrene. The catalyst can be a basic or neutral catalyst and can be a basic or neutral zeolite. The catalyst may comprise one or more promoters selected from the group of alkali elements, alkaline earth metal elements, rare earth elements, Y, Zr, and Nb.

The present invention has the effect of providing a method for producing styrene from toluene and methanol.

1 is a diagram illustrating a flow chart for the production of styrene by reaction of formaldehyde and toluene, in which formaldehyde is first produced in a separate reactor by dehydrogenation or oxidation of methanol to produce styrene. Reacts with toluene.
2 is a schematic diagram illustrating one aspect of an embodiment of the present invention having performance for catalyst regeneration and continuous reaction.

Toluene was used to produce styrene by reaction with methanol or methane / oxygen in co-feed. Theoretically, methanol (CH ₃ OH) and toluene (C ₆ H ₅ CH ₃ ) react together to produce styrene, water, and hydrogen gas, as shown below:

CH ₃ OH + C ₆ H ₅ CH ₃ → C ₈ H ₈ + H ₂ O + H ₂

In practice, however, methanol (CH ₃ OH) is often dehydrogenated to formaldehyde (CH ₂ O) and hydrogen gas (H ₂ ). Often the process cannot be economical because the toluene conversion is low or the selectivity for the production of methanol is too low. Conversion of methanol to COx or methane can result in unwanted byproduct streams that are not easily recovered. In order to avoid such unwanted side reactions, a process for producing styrene converting methanol to formaldehyde using a separate reactor is disclosed. Toluene then reacts directly with formaldehyde to produce styrene and water. Such a process can avoid unstable aspects of methanol.

Formaldehyde may be produced by oxidation or dehydrogenation of methanol. Silver-based catalysts are most commonly used in this process, but copper may also be used. Iron-molybdenum-oxide catalysts are typically used for dehydrogenation routes. Separate processes for the dehydrogenation or oxidation of formaldehyde of methanol can be used.

A separation unit can then be used if necessary to separate formaldehyde from hydrogen gas or water from unreacted methanol and formaldehyde prior to reaction with toluene for the production of styrene. This separation prevents formaldehyde from being hydrogenated back to methanol. The purified formaldehyde can then be sent to the first reactor and the unreacted methanol can be recycled. The use of formaldehyde for side chain alkylation of toluene is shown below:

CH ₂ O + C ₆ H ₅ CH ₃ → C ₈ H ₈ + H ₂ O

Formaldehyde is produced by the oxidation of methanol, which produces formaldehyde and water. The oxidation of methanol is shown in the following scheme:

2CH ₃ OH + O ₂ → 2CH ₂ O + 2H ₂ O

Or formaldehyde may be produced by dehydrogenation of formaldehyde and methanol to produce hydrogen gas. This method produces a preferred dry formaldehyde stream because it does not require separation of water prior to the reaction of toluene with formaldehyde. This dehydrogenation reaction is shown in the following scheme:

CH ₃ OH → CH ₂ O + H ₂

In order to prevent the hydrogenation of formaldehyde back to methanol, it is preferred to separate formaldehyde from water or hydrogen gas prior to reaction with toluene. Separation of formaldehyde from the remaining byproducts of the oxidation or dehydrogenation reaction yields a stable formaldehyde stream that can be used in the production of styrene.

Although the reaction has a 1: 1 molar ratio of toluene and formaldehyde, the ratio of feedstream is not limited in the present invention and may vary depending on the efficiency and operating conditions of the reaction system. If excess toluene or formaldehyde is fed to the reaction zone, the unreacted portion can be continuously separated off and recycled back to the process. In one embodiment, the ratio of toluene: formaldehyde may range from 100: 1 to 1: 100. In another embodiment, the ratio of toluene: formaldehyde is 50: 1 to 1:50; 20: 1 to 1:20; 10: 1 to 1:10; 5: 1 to 1: 5; It may range from 2: 1 to 1: 2.

1 is a simplified flow chart of one embodiment of the styrene manufacturing process mentioned above. The first reactor 2 is a dehydrogenation reactor or an oxidation reactor. This reactor was designed to convert the first methanol feed (1) to formaldehyde. The gaseous product 3 of the reactor is sent to a gas separation unit 4 in which formaldehyde is separated from unreacted methanol and unwanted byproducts. Any unreacted methanol 6 is then recycled back to the first reactor 2. By-product 5 is separated from clean formaldehyde 7.

In one embodiment, the first reactor 2 is a dehydrogenation reactor that produces formaldehyde and hydrogen and the separation unit 4 is a membrane capable of removing hydrogen from the product stream 3.

In yet another embodiment, the first reactor 2 is an oxidation reactor producing a product stream 3 comprising formaldehyde and water. The product stream 3 comprising formaldehyde and water can then be sent to the second reactor 9 without the separation unit 4.

The formaldehyde feed stream 7 then reacts with the feed stream of toluene 8 in the second reactor 9. Toluene and formaldehyde react to produce styrene. The product 10 of the second reactor 9 is then sent to any separation unit 11 where unwanted byproducts 15 such as water can be separated from styrene, unreacted formaldehyde and unreacted toluene. Can be. Unreacted formaldehyde 12 and unreacted toluene 13 may be recycled back to the reactor. The styrene product stream 14 may be removed from the separation unit 11 and provided for subsequent processing or processing if desired.

The operating conditions of the reactor and separator will be system specific and may vary depending on the composition of the feedstream and the product stream. The reactor 9 for the reaction of toluene and formaldehyde will operate at high temperatures and pressures such as, but not limited to, 250 ° C. to 750 ° C. and 1 atm to 70 atm and may include a basic or neutral catalyst system.

Suitable catalysts for the reaction of toluene and formaldehyde may include, but are not limited to, the following metal oxides: CuO; ZnO-CuO; ZnO-CuO-Al ₂ O ₃ ; CuCr ₂ O ₃ ; ZnCr ₂ O ₃ ; ZnCr ₂ O ₃ ; Or ZnO-CuO-Cr ₂ O ₃ . Other catalysts that may be used include metals supported on a substrate, such as silica or titania, such as: Ru; Rh; Ni; Co; Pd; Or Pt. They may also include accelerators such as Mn, Ti, Zr, V, Nb, K, Cs, or Na. Another group of catalysts that can be used in the present invention include sulfide based catalysts such as: MoS ₂ ; WS ₂ ; Mo ₂ WS ₂ ; CoMoS ₂ ; Or NoMoS ₂ . Such sulfide catalysts may include catalysts such as K, Rb, Cs, Ca, Sr, Ba, La or Ce.

The catalyst may have a toluene catalyst added such as alkali, alkaline earth metal and / or rare earth elements. Other toluene catalysts that may be added include Y, Zr, and / or Nb.

Improvements in side chain alkylation selectivity can be achieved by treating the molecular sieve zeolite catalyst with a suitable chemical compound that inhibits external acid groups and minimizes aromatic alkylation on the ring position. Another means for improving side chain alkylation selectivity may be to add a restriction on the catalyst structure that facilitates side chain alkylation. In one embodiment, the catalyst used in one embodiment of the present invention may be a basic or neutral catalyst.

Catalytic reaction systems suitable for the present invention may include one or more of zeolites or amorphous materials adapted for side chain alkylation selectivity. Non-limiting examples can be zeolites promoted with one or more of the following: Ru, Rh, Ni, Co, Pd, Pt, Mn, Ti, Zr, V, Nb, K, Cs or Na.

Zeolite materials suitable for the present invention may include silicate-based zeolites and amorphous compounds such as faujasite, mordenite, pentasil, and the like. The silicate-based zeolites are formed by alternating SiO ₂ and MO _x tetrahedrons, where M is an element selected from Groups 1-16 of the Periodic Table (New IUPAC). This type of zeolite has an 8-, 10-, or 12-membered oxygen ring channel. One example of the zeolites of the present invention is ZSM-5. 10- and 12-membered ring zeolites such as ZSM-11, ZSM-22, ZSM-48, ZSM-57 and the like.

Embodiments of reactors that may be used in the present invention may include, but are not limited to, fixed bed reactors, fluid bed reactors; And an entrained bed reactor. Reactors that are capable of high temperatures and pressures as described herein and that allow for contact of the catalyst with the reactants can be contemplated within the scope of the present invention. Embodiments of a particular reactor system may be determined by one skilled in the art based on specific design conditions and throughput, and do not imply any limitation in the scope of the present invention. One example of a fluidized bed reactor with catalytic regeneration capacity that can be employed in the present invention is shown in FIG. This kind of reactor system employing a riser can be modified as needed, for example by insulating or heating the riser if heat input is required or by covering the riser with coolant if heat dissipation is required. This design can be used to replace the catalyst during operation by removing the catalyst from the regeneration tube from the exit line or adding new catalyst to the system during operation.

2 is a schematic illustration according to an embodiment of the present invention having the performance of continuous reaction with catalyst regeneration. The reaction process 20 generally includes two main zones for reaction 21 and regeneration 22. The reaction zone may consist of a vertical or riser 23 as the main reaction site, with the discharge of the conduit emptied into a bulk process vessel, which may be referred to as a separation tube 24. In the reaction riser 23, a feed stream 25, such as toluene and formaldehyde, is connected with a fluidization catalyst, which may be a fluidized bed of catalyst relatively at reactor conditions. The residence time of the catalyst and hydrocarbons in the riser 23 necessary for the substantial completion of the reaction may vary as needed for the specific reactor design and throughput design. The flowing vapor / catalyst stream leaving riser 23 proceeds from the riser to a solid-steam separation device, such as a cyclone 26, which is usually located in and on top of separation vessel 24. The product of the reaction may be separated from the portion of the catalyst carried by the vapor stream by one or more cyclones 26 and the product may exit the cyclone 26 and the separation vessel 24 via line 27. The spent catalyst falls into stripper 28 located at the bottom of separation vessel 24. The catalyst may be conveyed to the regeneration vessel 22 along a conduit 29 connected to the stripper 28.

The catalyst can be continuously circulated from the reaction zone 21 to the regeneration vessel 22 and back to the reaction zone 21. The catalyst can therefore act as a transporter for the transfer of heat from zone to zone as well as the required catalytic activity. The catalyst from the reaction zone 21 delivered to the regeneration zone 22 may be referred to as a "consumed catalyst". The term "consumed catalyst" is not intended to indicate a total lack of catalytic activity by the catalyst particles. The catalyst discharged from the regeneration vessel 22 may be referred to as a "regenerated" catalyst. The catalyst may be regenerated in the regeneration vessel 22 by heat and may be connected to the regeneration stream 30. Regeneration stream 30 may comprise oxygen and may comprise steam. The regeneration catalyst may be separated from the regeneration stream using one or more cyclones 31, which may be removed from regeneration vessel 22 via line 32. The regenerated catalyst may be conveyed through line 33 to the bottom of riser 23 which is in contact with feed stream 25 again and may rise to riser 23.

It is to be understood that the use of a broader term, including, including, having, etc., provides support for narrower terms such as consisting of, consisting essentially of, consisting substantially of, and the like.

The term “molecular seive” is a fixed, open-network structure, usually that can be used to separate hydrocarbons or other mixtures by selective occlusion of one or more components, or can be used as a catalyst in catalytic conversion processes. Refers to a substance having a crystalline agent.

The use of the term "optionally" with respect to the elements of a claim is intended to mean that a main element is required or not required. Two alternatives may be within the scope of the claims. It is to be understood that the use of a broader term, including, including, having, etc., provides support for narrower terms such as consisting of, consisting essentially of, consisting substantially of, and the like.

The term "regenerated catalyst" refers to a catalyst that has recovered sufficient activity that is efficient in a particular process. This efficiency is determined by the individual process parameters.

The term "consumed catalyst" refers to a catalyst that has lost catalytic activity that is no longer efficient in certain processes. This efficiency is determined by the individual process parameters.

The term "zeolite" refers to a molecular sieve containing, for example, a silicate lattice usually associated with some aluminum, boron, gallium, iron and / or titanium. Throughout the description and the present disclosure, the terms molecular sieve and zeolite will be used more or less alternately. Those skilled in the art can also apply the idea associated with zeolites to general materials called molecular sieves.

Depending on the content, all references mentioned in this "invention" may refer only to certain detailed embodiments. In other instances, the content may be one or more of the above, but all need not be claimed. The information in this patent may include embodiments, modifications, and examples of the invention, including those that can be used and used by those skilled in the art when combined with useful information and techniques, but the invention is directed to such specific embodiments, modifications, And it is not limited to the example. Other and further embodiments, variations, and examples of the invention can be devised without departing from the scope of the invention, which is defined by the claims.

Claims (21)

In the method for producing styrene,
Converting methanol into formaldehyde in one or more first reactors to form a first product stream comprising formaldehyde,
Reacting toluene with formaldehyde in one or more second reactors to form a second product stream comprising styrene
A method for producing styrene, comprising. The method of claim 1, wherein the first product stream further comprises one or more of hydrogen, water, or methanol. The process of claim 1 wherein methanol is separated from the first product stream and recycled to the one or more first reactors. The method of claim 1, further comprising using one or more oxidation reactors to convert methanol to formaldehyde and water to form the first product stream. The method of claim 1, further comprising using one or more dehydrogenation reactors to convert methanol to formaldehyde and hydrogen to form the first product stream. The method of claim 1, wherein the second product stream further comprises one or more of toluene, water, or formaldehyde. The process of claim 1 wherein toluene is separated from the second product stream and recycled to the one or more second reactors. The method of claim 1, wherein formaldehyde is separated from the second product stream and recycled to the one or more second reactors. The method of claim 1, wherein the at least one second reactor comprises a reaction zone at reaction conditions comprising a catalyst for reacting toluene with formaldehyde to form styrene. The method of claim 1, further comprising sending the first product stream to a separation step for separating formaldehyde from the first product stream. In the method for producing styrene,
Converting methanol into formaldehyde in one or more first reactors to form a first product stream comprising one or more of formaldehyde, hydrogen, water, or methanol,
Sending the first product stream to a first separation step to separate formaldehyde from the first product stream;
Reacting toluene with formaldehyde in one or more second reactors to form a second product stream comprising one or more of styrene, toluene, water, or formaldehyde, and
Sending the second product stream to a second separation step to separate styrene from the second product stream.
A method for producing styrene, comprising. The process of claim 11, wherein methanol is separated from the first product stream and recycled to the one or more first reactors. The method of claim 11, wherein toluene is separated from the second product stream and recycled to the one or more second reactors. 12. The process of claim 11 wherein formaldehyde is separated from the second product stream and recycled to the at least one second reactor. 12. The method of claim 11, further comprising converting methanol into formaldehyde and water using one or more oxidation reactors to form the first product stream. The method of claim 11, further comprising converting methanol into formaldehyde and hydrogen using at least one dehydrogenation reactor to form the first product stream. The method of claim 16, wherein the first separation step comprises a membrane that removes hydrogen from the first product stream. 12. The method of claim 11, wherein said at least one second reactor comprises a reaction zone at reaction conditions containing a catalyst for reacting toluene with formaldehyde to form styrene. 19. The method of claim 18, wherein the catalyst is a basic or neutral catalyst. 19. The method of claim 18, wherein the catalyst is a basic or neutral zeolite. 19. The method of claim 18, wherein the catalyst comprises one or more promoters selected from the group of alkali elements, alkaline earth metal elements, rare earth elements, Y, Zr, and Nb.

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